Excessive daytime sleepiness (EDS) and fatigue are some of the most frequent symptoms in neurological diseases and could impact on quality of life by increasing the risk of accidents and generally affecting daily life activities. In this review, we will examine the variety of causes responsible for EDS in neurological diseases, including nocturnal sleep alterations, CNS pathological abnormalities with alterations in arousal and/or REM regulation systems, circadian rhythms disorders, drugs, and comorbid psychiatric or primary sleep disorders. Among neurological diseases, epilepsy, dementia, Parkinson disease, multiple sclerosis, and myotonic dystrophies represented a model for these interactions between EDS and neurological diseases. A complete diagnostic workup in neurological patients with EDS should be undertaken since EDS can worsen many different aspects such as psychiatric symptoms, cognitive deficit, and in some cases, the severity of the neurological disease per se. Moreover, quality of life and risk of accidents are dependent on EDS. An individualized approach to this symptom in neurological patients should be considered with a focus on modifiable causes such as SDB, psychiatric comorbidities, and drugs. When considering EDS and fatigue in neurological diseases, close attention to lifestyle and sleep hygiene is advisable. A critical review of ongoing pharmacological therapy should not be overlooked. Possible diagnosis and treatment of SDB should be always considered.